This application claims the priority of German Patent Applications Ser. Nos. 101 20 923.1, filed on Apr. 30, 2001 and 101 60 167.0, filed on Dec. 07, 2001. The disclosures of the above German priority applications and of each and every U.S. and foreign patent and patent application mentioned below are incorporated herein by reference.
The present invention relates to a device for producing zones of desired air permeability in the enveloping material of rod-shaped articles, in particular rod-shaped articles in the tobacco-processing industry. The invention relates to a beam guiding arrangement for focussing an energy-rich beam produced by a radiation source onto the enveloping material to form a number of perforation zones, wherein the number of perforation zones corresponds to the number of partial beams. The invention furthermore relates to a multiple beam-generating device that generates a multiple beam from a single beam. The invention also relates to a beam divider, in particular for use in such a device, for dividing a beam generated by a radiation source into at least two partial beams. Finally, the invention relates to a method for producing zones of desired air permeability in the enveloping material of rod-shaped articles, particularly in the tobacco-processing industry. Such a method comprises the steps of focusing an energy-rich beam, produced by a radiation source, onto the enveloping material in order to form perforation zones and to generate a multiple beam from a single beam.
Rod-shaped articles in the tobacco-processing industry in this connection are understood to include all articles provided with a perforation during production or following production. Above all, this refers to filter cigarettes, but can also refer to other types of cigarettes, other rod-shaped smoking articles or filter rods. The enveloping material is understood to include tape used for enveloping tobacco ropes or filter ropes, covering paper tape or sheets and the like, which can be perforated in the form of a material web, ready-to-use sections or as enveloping material for the rod-shaped articles.
Perforating the enveloping material for cigarettes and other rod-shaped smoking articles creates a zone of desired air permeability, through which the smoker suctions in air from the side while smoking. As a result, the shares of nicotine and condensate in the smoke are influenced, which also affects the taste. A laser is preferably used for perforating the enveloping material. The radiation from this laser is guided via an optical beam-guiding device into the respective perforation zones where it inserts the desired holes into the enveloping material.
With the aid of the multiple beam-generating device, it is possible to generate double or multiple beams for producing at least two side-by-side arranged perforation tracks in one and the same perforation zone, wherein the perforation tracks jointly form a perforation pattern in the perforation zone. Through a corresponding guidance and modulation of the double or multiple beams, different perforation patterns can be created in dependence on the desired requirements. One advantage of forming the perforation patterns with several side-by-side arranged perforation tracks is that the desired perforation can be realized over a specified surface and with a specific lengthwise expansion.
German Patent document 195 30 216 A1 discloses a device of the aforementioned type that uses a single laser as the radiation source. The multiple beam-generating device of the known device consists of a beam divider and deflection mirrors, used to generate two beams from the single beam emitted by the radiation source. Modern cigarette machines initially produce double-length cigarettes, which are then cut into individual cigarettes. As a result, the covering paper tape that connects the tobacco rods with the filter segments, or the connected double-length cigarettes, must be perforated in two perforation zones, so that each individual cigarette is provided with a corresponding perforation zone. The double or multiple beams of the known device are therefore additionally divided into respectively two partial beams with the aid of the beam divider. The beam guiding arrangement of this known device is provided with at least one additional deflection mirror. Thus, the known device generates two beams, which are converged in the joint perforation zones to form respectively one multiple beam. In addition, the beam-guiding device requires a specific optical arrangement for focusing the beams in the perforation zones onto the side-by-side extending perforation tracks. It is important that the double or multiple beams are guided at a specific and rather acute angle onto the beam divider of the beam-guiding device, which requires an exact adjustment of the beam divider and the deflection mirrors for the multiple beam-generating device.
It is an object of the invention to provide a different device and a different method of the aforementioned type.
The above and other objects are achieved according to the invention by the provision of a device for producing zones of desired air permeability in the enveloping material of rod-shaped articles, comprising: a beam-guiding device for focusing a multiple beam generated from a single energy-rich beam originating from a radiation source onto the enveloping material in order to create perforation zones; and a multiple beam-generating device located for creating a multiple beam from the single energy-rich beam, the multiple beam-generating device comprising at least one optical element that is fixed relative to the single energy-rich beam in an operating position of the optical element.
Thus, the foregoing and other objects are solved according to the invention in that the multiple beam-generating device of a device of the aforementioned type is provided with at least one optical element that is fixed in its operating position, relative to the beam from the radiation source.
Optical elements of this type are available for generating the desired multiple beams. With the aid of the invention, it is possible to realize a simple multiple beam-generating device and, in the process, essentially omit all moving optical elements, and those optical elements susceptible to movement, as well as complex optical arrangements. The diffractive optical element can be arranged in the beam path, either before or after the beam-guiding device.
A diffractive optical element in particular is capable of generating the desired slightly diverging double or multiple beams from a single beam, preferably generated by a single source, without requiring additional separate optical elements that may have to be adjusted.
To be sure, the use of diffractive optical elements in a device of the aforementioned type is known from German Patent document 195 11 393 A1 and European Patent Application No. 0 761 376 A1. However, the diffractive optical elements for the known prior art devices are components of the beam-guiding device and are used in the beam-guiding device in particular as beam dividers for dividing the double and multiple beams existing therein. The multiple beam-generating devices of the known systems are composed of different optical elements and thus provide a different type of structural solution. The prior art does not provide a stimulus for using a diffractive optical element, in addition to or in place of the beam-guiding device, either in the multiple beam-generating device or in place of it for generating double or multiple beams before they enter the beam-guiding device. The invention therefore cannot suggest itself as a result of the prior art.
An optical grid is particularly suitable for use as diffractive optical element.
A different advantageous embodiment is provided with an optical element that generates a multiple beam with an even number of partial beams, which exit at an angle relative to each other. This embodiment is distinguished by an optical element designed so that a first partial beam of the multiple beam exits in the direction of or along the axis of the beam entering the optical element and that the additional partial beam(s) of the multiple beam exits (exit) the optical element at an angle to the direction or axis of the beam entering the optical element. This design makes use of the knowledge that a stray beam as a rule develops unavoidably in the direction of the beam path for the incident beam. With the present design, the stray beam is cleverly used to form the first partial beam itself, so that the stray beam no longer interferes, but is useful. The first partial beam that is essentially formed by the stray beam and exits the optical element in the direction of the beam path axis for the incident beam therefore is not diffracted and can be called a partial beam of zero diffraction order. The second partial beam can be called a partial beam of the first diffraction order and additional partial beams can, if applicable, be called partial beams of the nth diffraction order.
The optical element preferably generates a multiple beam with two partial beams that diverge at an angle to each other, wherein the optical element is designed such that the first partial beam of the multiple beam exits in the direction or along the axis of the beam entering the optical element and thus forms the partial beam with zero diffraction order. The second partial beam exits at an angle to the direction or the axis of the beam entering the optical element and thus forms the partial beam of the first diffraction order. For this, the optical element should advantageously be designed such that an additional partial beam that is mirror-symmetrical to the second partial beam, relative to the axis, is essentially suppressed. The additional partial beam that must be suppressed is a partial beam of the 1st diffraction order. The additional partial beams of the 2nd to the nth diffraction order can, if necessary, be suppressed in the same way.
The previously specified object is furthermore solved according to the invention in that for a method of the aforementioned type, the beam is fanned out in a diffractive optical element into an even number of partial beams that diverge at an angle to each other in order to form the multiple beam.
The optical element should be arranged such that it can be removed from the beam path. An arrangement of this type is advantageous for exchanging, for example, the optical element in view of different requirements. This embodiment is furthermore advantageous if it is desirable to insert a single perforation track into the perforation zone in place of several side-by-side extending perforation tracks. In that case, the optical element can be removed easily and is ineffective when swiveled out of the beam path. Finally, removing the optical element will also simplify the maintenance. The optical element preferably should be arranged such that it can be pivoted from the beam path. In the first position where it is pivoted into the beam path, the optical element effectively generates the double and multiple beams. In this first position, the optical element according to the invention is fixed relative to the beam path, meaning to the beam generated by the radiation source.
The beam-guiding device is normally installed inside a housing, which can also be called a beam-divider head. In a case of that type, it is advantageous if a holding element for holding the optical element is provided on or inside the housing. The optical element should preferably sit on the holding element, so that the optical element is supported by the holding element.
For the previously mentioned reasons, the holding element should be mounted on or in the housing such that it can be detached again.
The holding element should be arranged so as to be movable inside the housing and should be pre-stressed with a spring in the direction away from the housing. This embodiment is advantageous if the housing is flanged with the side that supports the holding element to a machine, since the holding element is then secured relative to such a machine through the pre-stressing.
Means for detecting the presence of the housing and/or the holding element can preferably be provided when arranged on a machine for producing rod-shaped articles. This arrangement has technological advantages for the production process.
The holding element for another embodiment that is particularly preferred at present is a tube through which the radiation is guided and which preferably has the optical element installed at the tube end that facing the beam-guiding device. For an easier handling, it should be possible to fit the tube into the housing.
The beam-guiding device should advantageously have optical focusing means, designed to generate converging beams and to focus these onto the perforation zones on the enveloping material.
Another embodiment, which is particularly preferred at present and for which the multiple beam-generating device forms a multiple beam from the single beam emitted by the radiation source, is provided with a beam divider that divides the multiple beam into at least two partial beams. The beam-guiding device focuses the partial beams from the beam divider onto the enveloping material for creating perforation zones, wherein the number of perforation zones corresponds to the number of partial beams. This embodiment distinguishes itself in that the multiple beam-generating device consists of a single optical element that is fixed in its operating position relative to the beam from the radiation source. A single optical element is thus provided for this embodiment, which is installed in the beam path in front of the beam-guiding device.
The optical element can also be arranged in the beam path in front of the beam divider. The optical element in that case should basically be arranged as close as possible to the beam divider, meaning at the shortest distance thereto, to avoid excessive divergence of the double or multiple beams generated by the optical element before they enter the beam divider. There, they are divided into one or several partial beams, are subsequently transmitted further by the beam-guiding device and are again converted to converging partial beams for focusing onto the perforation zones.
The optical element for this embodiment can alternatively also be integrated into the beam divider of the beam divider arrangement, thus making it possible to keep the required space as small as possible. The beam divider simultaneously can also form the optical element, so that only a single optical component can be provided, which combines the functions of beam divider and optical element. An integrated beam divider of this type otherwise forms a separate aspect of the invention.
A further alternative embodiment of the invention is provided with a beam divider arrangement that divides the energy-rich beam generated by the radiation source into at least two partial beams. For this, beam-guiding device focuses the partial beams onto the enveloping material in order to generated a number of partial beams corresponding to the number of perforation zones, wherein the multiple beam-generating device forms a multiple beam from each partial beam. The multiple beam-generating device of this embodiment is distinguished in that it has an optical element for each partial beam, which is fixed in its operating position relative to the respective partial beam, wherein the multiple beam-generating device is generally arranged in the beam path behind the beam divider arrangement. Since a separate optical element is provided for each partial beam, the multiple beam-generating device of this embodiment still has a number of optical elements that correspond to the number of partial beams.